The present invention relates to a portable, self-contained, X-ray apparatus that digitally acquires, processes, displays, stores, and/or transmits electronic radioscopic images of sealed packages, containers and other objects, including patients, on location for security, customs, medical, and other non-destructive and non-invasive purposes. More particularly, the present invention provides an improved clocking and digitization system for use with a portable X-ray radioscopic imaging system to enhance the spatial quality and contrast sensitivity of an on-chip integrated image of an otherwise conventional charge-coupled device (CCD) camera by employing the direct clocking of pixels and correlated digitization of their signals within the camera head.
Some of the general concerns and problems associated with portable, digital X-ray apparatus for producing, storing and displaying electronic radioscopic images are set forth in U.S. Pat. No. 5,608,774, incorporated herein by reference. The '774 patent sets forth a system in which a pulsed X-ray source transmits a burst of narrow pulses of X-rays at the object being investigated at a low repetition rate. The X-ray sensor utilizes an X-ray scintillating screen in combination with either an integrating CCD camera, or an active matrix of thin film transistors and sample-and-hold photodiodes, to produce an integrated signal representative of the accumulated number of X-ray pulses that are sensed in a given pixel area of the scintillating screen. The self-contained display and controller unit utilizes digital signal processing within an enhanced portable computer, including a flat solid state display panel and associated drive circuitry, in order to display the full dynamic range and resolution of the sensor. A modem allows the digitized image to be sent to a remote location where the exact same image can be recreated for analysis by off-site experts, e.g., via an internal ethernet LAN, intranet, or internet connection.
Presently, an analog CCD Video camera puts out standard RS-170 waveform. Each line must be read out in approximately 63.5 microseconds in an interlaced format. A conventional CCD camera employing an analog video readout is modified to suppress normal blanking and readout of CCD until sufficient flux is integrated onto chip to provide a full scale output signal. At this point, the system then waits until the beginning of the next active interlaced field (odd or even) and then reads out the following two successive fields to a digitizer remotely located at the computer display unit. It would be desirable therefore, to address the specific problems associated with analog CCD Video cameras to provide improved signal to noise and resolution for the CCD camera over currently used video based X-ray imagers.
There are many instances in the medical, security or customs field when it is necessary to examine or inspect, in a non-invasive way, a patient, animal, or other living organism; or to examine and inspect, in a non-destructive way, the contents of a closed package, box, suitcase, or other container. For example, customs departments are routinely charged with the responsibility of inspecting the contents of incoming packages to make sure such packages do not contain explosives, drugs or other contraband. Similarly, terrorists, criminals, or other enemies frequently carry out their criminal acts of terrorism or war by planting bombs in sealed containers or packages, and then sending the sealed containers/packages to the intended victims, e.g., through the mail, or planting the sealed container/packages at the desired target, e.g., by leaving a locked suitcase or a sealed box containing a bomb in a busy public transportation terminal. When security personnel encounter suspicious packages or other containers being sent through the mail, or left at public transportation terminals, or other locations, they must perform a careful inspection of such containers to ascertain their contents.
When suspicious containers, such as suitcases, sealed boxes/packages are discovered, they generally must be examined or inspected on location in a non-destructive manner. If the non-destructive examination reveals the presence of explosives (e.g., a bomb) or contraband (e.g., drugs), then the container and its contents must be safely disposed of. If, on the other hand, the examination reveals the absence of explosives or contraband, then the container may be handled in a normal manner, i.e., forwarded on to its owner or addressee.
Unfortunately, the process used to examine or inspect a suspicious sealed box, package, suitcase or other container must not trigger any bomb that may be concealed inside. Thus, for example, as a safety precaution, the suspicious container may not be opened because such opening may trigger any bomb contained therein. Similarly, the suspicious container may not be moved because such movement could likewise trigger a hidden bomb. Further, the suspicious container may not be examined with high doses of radiation because such radiation, if significantly greater than normal background radiation, could also trigger a hidden bomb. What is needed, therefore, is a non-invasive technique for inspecting the contents of a suspicious container without requiring that the container be opened, moved, or subjected to high levels of radiation.
Heretofore, suspicious containers of the type referenced above have been examined using portable, generally low power, X-ray generators and highly sensitive X-ray film as a detector, with many attendant problems. For example, the film used with such conventional film-based radiography systems has a poor shelf life in the environment typical to field inspections, which means that its sensitivity may vary considerably. The operator must then go back to the object under test for each image taken until the correct exposure and orientation is obtained. Once such image is taken, it must then be processed with a portable chemical laboratory with the attendant delays of such efforts.
It is also known in the art to improve the conventional film-based radiography systems by adapting certain types of industrial imaging systems as an image detection system to overcome some of the field problems. Such systems typically use intensified, low-light level cameras to record the image, and then conventional cathode ray tube (CRT) monitors to display the resulting X-ray images. Unfortunately, such systems are bulky and poorly suited for portable applications. Further, the CRT displays do not always provide the contrast needed to readily see the X-ray image in bright ambient light conditions. Further, while some limited image enhancement techniques have been applied to such existing systems, the output image is still simply a real-time analog CRT image.
The shortcomings of analog approaches are introduced by the constraints of the standard RS-170, video timing and waveforms as well as the need to filter the outputs of the discrete pixel outputs into a continuous waveform which must then be redigitized at the end of a long cable. This multiple conversions between digital and analog signals introduces a loss of modulation in the higher spatial frequencies which causes a corresponding loss of contrast in the reproduced images especially for the finer structure in the image. Moreover, putting the analog to digital converter at the computer requires that the analog signal be transmitted over a long cable with attendant loss of high frequency information further reducing the contrast of the fine structure in the image.